Off and on it is noticed that although the diagnosis of amoebic liver abscess is made, when aspiration is attempted, pus is not recovered from the expected site. This would usually occur in a patient who either has no amoebic liver abscess and the diagnosis is wrong or who has an abscess which is solid. (This has been discussed elsewhere).
But there are other patients with amoebic liver abscess where the difficulty is genuine. The following are few examples:

1. Figure 1 shows a huge enlarged left lobe diagnosed as left lobe amoebic liver abscess. On tapping the left lobe, no pus could be aspirated. Figure 2 shows the liver scan of the same patient which revealed that the patient had a right lobe abscess although the left lobe was markedly hypertrophied. Such a hypertrophy of the unaffected part of the liver is not uncommon and is possibly due to congestion or compensatory hypertrophy. We have since then realised that "point or intercostal tenderness" is more important than "enlargement" in localizing an amoebic liver abscess. The patient mentioned above did have "intercostal tenderness" in the midaxillary line but the left lobe, though enlarged, was not markedly tender.
2. As mentioned elsewhere, quite often we have diagnosed a superior surface abscess because of marked elevation of the right dome of the diaphragm (Fig. 3) when the scan showed a huge inferior surface abscess. This abscess had thus pushed the upper part of the right lobe and elevated the right dome. We have now realised that (a) absence of a history of pain in the shoulder area at any time during the illness, (b) lower intercostal tenderness, (c) marked tender subcostal enlargement of the right lobe (d) a clean elevated right dome with diminished mobility but notcomplete immobilisation and (e) no obliteration of the costo- or cardiophrenic angle-all the above findings are in favour of an inferior surface abscess even if the right dome is elevated.
3. Off and on we have diagnosed a superior surface right lobe abscess and the scan has demonstrated a posterior surface abscess, with the superior surface looking absolutely free of the disease. Point tenderness in the loin has off and on helped us not to make the above mistake. In these cases the right dome was not only elevated, but had a fuzzy outline and the right costophrenic angle was obliterated. It is important to realise this situation because in such patients aspiration when done in the scapular line posteriorly is most rewarding.
4. On many occasions the lower margin of the liver cannot be palpated because of the localised guarding of the muscles. Such patients then, most probably, have an inferior surface abscess. This can be confirmed by seeing a normal right dome of the diaphragm in an X-ray chest. But if the right dome turns out to be markedly abnormal, it should not be forgotten that a superior surface abscess can rarely leak into the peritoneal cavity.
5. Superior surface abscess does not always produce shoulder pain or the pain may be felt a few days after the onset of the illness. Sometimes one could miss a superior surface abscess because the right dome looks normal; but if a lateral view is taken, a hump may be seen posteriorly. I have also seen patients showing superior surface abscess, on the liver scan, when the right dome of the diaphragm showed no significant changes. Regarding pain around the right shoulder, often I have seen patients who experience it for one or two days initially and subsequently only on coughing or taking deep breaths. Many patients describe it as a discomfort rather than pain. Others experience it much later in the course of the illness. On rare occasions, we have seen patients with a posterior surface abscess complaining of pain in the right shoulder.
6. After diagnosing an inferior surface amoebic liver abscess clinically, chest X-ray should still be asked for to pick up a second abscess if present. As in rheumatic heart disease (e.g. mitral stenosis with aortic incompetence) where one lesion is usually dominant, similarly in patients with two amoebic liver abscesses, often one produces more signs and the other is dormant.
7. Once in a while one comes across a patient who has been diagnosed as an appendicular abscess but on laparotomy, pus is discovered which has leaked from an amoebic liver abscess along the paracolic gutter into the right iliac fossa! This may be a very good example of an 'extrahepatic' amoebic liver abscess, a term used by DeBakey and Jordan.¹
8. Lastly, there are patients of amoebic liver abscess with either marked or minimal diffuse tenderness or multiple point tenderness or a combination of the two. It is then difficult to locate the site of the abscess. If the lower margin of the right and left lobe is not palpable then an inferior surface abscess is not likely. Percussion for the upper border and eliciting tenderness in the loin would help further. X-ray chest (P.A. and right lateral views) should be asked for to see the details of the right dome of the diaphragm. These are the cases where a liver scan is of great help.
   False localisation is more of a problem in institutions where liver scanning is not being done. Once the liver scan is available, what you see on the scan is of course more reliable, than the clinical signs and symptoms. Off and on we have experienced limitations in the localisation of an amoebic liver abscess clinically. This does not mean that the clinical examination and X-ray chest should receive less importance for localisation of an amoebic liver abscess. Moreover it should always be remembered that localisation is the second step in the evaluation of a patient. The first is to suspect an amoebic liver abscess clinicallv.

References:

1. DeBakey, ME and Jordan, GL, Surg Clin N. Am., 1977 57, 325